Nullable<T>.HasValue Property

Gets a value indicating whether the current Nullable<T> object has a value.

Property Value

Type: System.Boolean
true if the current Nullable<T> object has a value; false if the current Nullable<T> object has no value.

' This code example demonstrates the Nullable(Of T).HasValue 
' and Value properties.
Class Example
 Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
 Dim myNow As Nullable(Of DateTime)
 ' Assign the current date and time to myNow then display its value.
 myNow = DateTime.Now
 Display(outputBlock, myNow, "1) ")
 ' Assign null (Nothing in Visual Basic) to myNow then display its value.
 myNow = Nothing
 Display(outputBlock, myNow, "2) ")
 End Sub 'Main
 ' Display the date and time.
 Public Shared Sub Display(ByVal outputBlock As System.Windows.Controls.TextBlock, ByVal displayDateTime As Nullable(Of DateTime), _
 ByVal title As String)
 ' If the HasValue property for the nullable of DateTime input argument is true, 
 ' display the value of the input argument; otherwise, display that no value is
 ' defined for the input value.
 outputBlock.Text &= title
 If displayDateTime.HasValue = True Then
 outputBlock.Text += String.Format("The date and time is {0:F}.", displayDateTime.Value) & vbCrLf
 Else
 outputBlock.Text &= "The date and time is not defined." & vbCrLf
 End If
 End Sub 'Display 
End Class 'Sample '
'This code example produces the following results:
'
'1) The date and time is Tuesday, April 19, 2005 4:16:06 PM.
'2) The date and time is not defined.
'

// This code example demonstrates the Nullable<T>.HasValue 
// and Value properties.
using System;
class Example
{
 public static void Demo(System.Windows.Controls.TextBlock outputBlock)
 {
 DateTime? myNow;
 // Assign the current date and time to myNow then display its value.
 myNow = DateTime.Now;
 Display(outputBlock, myNow, "1) ");
 // Assign null (Nothing in Visual Basic) to myNow then display its value.
 myNow = null;
 Display(outputBlock, myNow, "2) ");
 }
 // Display the date and time.
 public static void Display(System.Windows.Controls.TextBlock outputBlock, DateTime? displayDateTime, string title)
 {
 // If a value is defined for the displayDatetime argument, display its value; otherwise, 
 // display that no value is defined.
 outputBlock.Text += title;
 if (displayDateTime.HasValue == true)
 outputBlock.Text += String.Format("The date and time is {0:F}.", displayDateTime.Value) + "\n";
 else
 outputBlock.Text += "The date and time is not defined." + "\n";
 }
}
/*
This code example produces the following results:
1) The date and time is Tuesday, April 19, 2005 4:16:06 PM.
2) The date and time is not defined.
*/

Nullable<T> Structure

System Namespace